Injection Molding
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Severe Internal Stress Concentration in EVOH
Problem Phenomenon
EVOH product internal stress >15MPa causing cracking during storage
Cause Analysis
Injection speed too fast, orientation stress large; uneven cooling freezing thermal stress; gate location improper, flow orientation concentrated
Solution
1) Reduce injection speed to decrease orientation; 2) Uniform mold temperature to reduce thermal stress; 3) Anneal at 80°C/4h to release stress; 4) Optimize gate location
Key Takeaway
Internal stress is caused by fast injection and uneven cooling; speed reduction, uniform cooling and annealing are key
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